The present invention relates to a lens array unit utilized in e.g. an image reading device. Further, the present invention relates to a method of manufacturing a lens array as part of the lens array unit, and to an optical device incorporating the lens array unit.
In an image reading device incorporated in a facsimile machine or a scanner, often, an image of the document is read without inversion nor magnification, by utilizing a plurality of light receiving elements disposed in a row. In this arrangement, the image of the document must be focused on the light receiving elements without inversion nor magnification, by utilizing a lens array provided by a plurality of image formation lenses. Conventionally for example, this is achieved by a lens array 9 as shown in FIG. 51 and FIG. 52, in which a plurality of lenses 91 are held by a resin support 90.
The lenses 91 are provided by a plurality of columnar selfoc lenses (rod lenses), each having a pair of flat lens surfaces 91a, 91b. However, each lens 91 has a unique optical characteristic that its refractive index varies in accordance with the distance from its axial center. As a result, as shown in FIG. 52, light which passes through the lens 91 takes a snaky route, and an object (axe2x86x92b) is projected in an non-inverted, non-magnified image (axe2x80x2xe2x86x92bxe2x80x2).
In the prior art, in order to manufacture the lens array 9, the lenses 91 are manufactured first. Next, by means of an insertion molding, the lenses 91 are embedded into the support 90 when the support is molded from resin.
However, the prior art has the following problem.
Specifically, first, since the lens 91 is a selfoc lens which has the unique optical characteristic as described above, manufacturing the lens is not an easy task. Without a special facility for making the selfoc lens, manufacture of the lens 91 is very difficult, which has increased manufacturing cost of the lens array 9.
Further, according to the above prior art, manufacturing of the lenses 91 is a separate process from the forming of the support 90. Thus, production efficiency of the lens array 9 has been low, increasing further the manufacturing cost of the lens array 9.
An object of the present invention is to provide a lens array unit and an optical device using the same, capable of eliminating or reducing the problems described above.
Another object of the present invention is to provide a method for appropriately manufacturing the lens array as a component part of the lens array unit.
A lens array unit provided by a first aspect of the present invention comprises: a first lens array including a plurality of first lenses each serving as a convex lens, and a first support holding the first lenses. The first lenses and the first support are formed integrally of a translucent resin. The lens array unit further comprises a second lens array including a plurality of second lenses each serving as a convex lens, and a second support holding the second lenses. The second lenses and the second support are formed integrally of a translucent resin. The first and the second lens arrays are placed, one on the other, with each of the first lenses in alignment with a corresponding one of the second lenses on a same axis, for formation of a non-inverted, non-magnified image.
The lens array unit having such an arrangement can be suitably used as a replacement of the prior art selfoc lens array, for application of forming a non-inverted, non-magnified image. Since each of the first and the second lenses is provided by a convex lens, unlike the selfoc lens, there is no need to vary the refractive index inside the lens. According to the present invention, each of the lenses in the first and the second lens arrays and the supports therefor can be easily formed by means of an ordinary resin injection molding technique. As a result, production efficiency of the lens array unit according to the present invention is high, making it possible to lower a cost of manufacture than in the lens array unit that uses the prior art selfoc lens.
Preferably, at least the first lens array, of the first and the second lens arrays, is provided with separating means for optical separation of the lenses from each other.
According to such an arrangement, it becomes possible to prevent a problematic crossing of light (optical cross talk) between the first lenses when the light passes through the first lens array. This makes it possible to form a clear image. When using the lens array unit according to the present invention, if an arrangement is made so that the light will first enter the first lens array, comes out of the first lens array and then enters the second lens array, the optical cross talk in the second lens array can be reduced to a certain extent even if the second lens array is not provided with the separating means, and this is already demonstrated.
Preferably, the separating means is provided only in the first lens array.
According to such an arrangement, manufacture of the lens array unit can be facilitated to the extent that the second lens array is not provided with the separating means.
Preferably, the separating means includes a light shield isolating the first lenses from each other.
According to such an arrangement, the light shield appropriately prevents the light from crossing each other between the first lenses.
Preferably, the light shield is capable of absorbing light received.
According to such an arrangement, it becomes possible to prevent light which has reached the light shield from being reflected back by the light shield, making it more desirable for forming a clear image.
Preferably, the light shield includes at least one recess provided in the first support for the isolation of the first lenses from each other.
According to such an arrangement, it becomes possible to prevent light from traveling between the first lenses, by the recess or the surface that defines the recess.
Preferably, the light shield further includes a dark material covering the surface which defines the recess. The word dark herein means a black color preferably, although this does not necessarily limit the present invention.
According to such an arrangement, the dark material appropriately blocks and absorbs the light which otherwise will get out of the first lens and then into an adjacent one.
Preferably, the first support includes a first surface, and a second surface away from the first surface at a distance in a direction of the axis""s of the first lenses and faced to the second lens array. Further, the recess is provided in at least one of the first and the second surfaces, without penetrating the first support.
Preferably, the recess is provided in each of the first and the second surfaces.
According to such an arrangement, even if the depth of the recess is relatively shallow, it is still possible to sufficiently prevent the optical cross talk between the first lenses. Therefore, the present arrangement is suitable when the recess cannot be made very deep.
Preferably, the recess is provided only in one of the first and the second surfaces.
According to such an arrangement, as compared with the above case in which the recess is provided in each of the first and the second surface, the number of the recesses can be smaller. This can facilitate an operation for forming the recesses.
Preferably, the separating means further includes a light shielding member covering the first surface of the first support.
According to such an arrangement, the light shielding member also offers the effect of preventing the optical cross talk between the first lenses. Further, this arrangement prevents light unnecessary for the image formation from entering the first lens array via the first surface. Therefore, it becomes possible to form a clearer image.
Preferably, the separating means further includes a light shielding member covering the second surface of the first support.
According to such an arrangement, it becomes possible to prevent light, which is unnecessary for the image formation, from entering the second lens array from the second surface. Further, this arrangement prevents such a phenomenon that light coming from one of the first lenses unwontedly enters a diagonal one of the second lenses. Therefore, it becomes possible to form a clearer image.
Preferably, each of the first lenses has an outer circumferential surface rising from the first support, and the light shield includes a dark material covering the outer circumferential surface.
According to such an arrangement, it becomes possible to reduce light, which is unnecessary for the image formation, from entering the first lens. Further, since the light within the first lens does not pass through the outer circumferential surface, it also is possible to reduce the optical cross talk between the first lenses.
Preferably, each plurality of the first and the second lenses are disposed in a straight row. Such an arrangement is suitable for an application of forming a line image.
Preferably, each plurality of the first and the second lenses are disposed in a plurality of rows having a narrow width and extending in a predetermined direction.
According to such an arrangement, too, a line image can be formed. In this case, as compared with the case in which there is only one row in each of the first and the second lenses, a greater amount of light can be introduced to an image formation region, and a brighter image can be obtained.
Preferably, the separating means includes a first recess provided in the first support for separation of the first lenses from each other in the predetermined direction. The separating means further includes a second recess provided in the first support for separation of the first lenses from each other in a direction across the predetermined direction, and a dark material covering surfaces which respectively define the first and the second recesses.
According to such an arrangement, the optical cross talk between the first lenses can be appropriately prevented in both of the predetermined direction and the direction across the predetermined direction.
Preferably, the first and the second recesses communicate with each other.
According to such an arrangement, it becomes possible to facilitate an operation of coating the surfaces that defines the first and the second recesses with the dark material.
Preferably, the first recess has a depth axially of the first lenses, deeper than a depth of the second recess.
According to such an arrangement, the first recess can block a greater amount of light than the second recess. This allows to achieve the following advantage that the amount of light that passes the first and the second lens arrays and then reaches the image formation region is smaller in the predetermined direction, but larger in a direction across the predetermined direction. With such a capability, it becomes possible to form a clear, well-focused image in the predetermined direction, whereas in the direction across the predetermined direction, it becomes possible to form a bright image. Therefore, as a total, it becomes possible to obtain a well-focused and bright image.
Preferably, the second support is provided with means for optical separation of the second lenses from each other only in the predetermined direction.
According to such an arrangement, again, it becomes possible to achieve the advantage that the amount of light that passes the first and the second lens array and then reaches the image formation region is smaller in the predetermined direction, but larger in the direction across the predetermined direction. Therefore, a similar effect can be achieved as achieved by the first arrangement in which the first recess is made deeper than the second recess.
Preferably, each plurality of the first and the second lenses are disposed in a matrix, for formation of an image having a predetermined area.
According to such an arrangement, the lens array can be suitably utilized in an application of forming an area of non-inverted, non-magnified image.
Preferably, the separating means includes at least one recess surrounding each of the first lenses, and a dark material covering a surface which defines the recess.
According to such an arrangement, if the first lenses for example are disposed in a matrix, it becomes possible to prevent the optical cross talk between octagonal pairs of the first lenses.
Preferably, the first and the second lens arrays are provided with at least one pair of recess and projection, and the first and the second lens arrays are fitted together by the pair of recess and projection.
According to such an arrangement, an operation of assembling the first and the second lens arrays in mutual alignment is facilitated.
Preferably, the first lenses have a longer axial length than the second lenses.
According to such an arrangement, when light that has passed the first lens comes to the lens surface of the second lens and enters the second lens, a greater amount of the light that travels in the second lens can reach the other lens surface of the second lens, to the extent that the second lens is made shorter. Therefore, it becomes possible to increase the amount of light that comes out of the second lens, making it more desirable to form a bright image. Further, by increasing the length of the first lens, it becomes possible to obtain a clear image. Specifically, the first and the second lenses each serving as a convex lens can give a non-inverted, non-magnified image of an object because light from the object is first received by the lens surfaces of the first lens and formed into an inverted, reduced image, and then this inverted, reduced image is increased and inverted back by the lens surfaces of the second lens. In such an arrangement, if the length of the first lens is increased, it becomes possible to obtain the inverted, reduced image at an image formation point closer to the lens surface of the first lens. Therefore, according to the present embodiment, unlike the case in which an inverted, reduced image reduced at a large reduction rate is magnified at a large magnification rate and inverted, the finally obtained image that is not inverted nor magnified is better protected from adverse effect such as lens surface distortion.
Preferably, the second lenses have a larger diameter than the first lenses.
Preferably, each of the first lenses includes a first lens surface and a second lens surface away from the first lens surface, and each of the second lenses includes a third lens surface closely facing the second lens surface and a fourth lens surface away from the third lens surface. Further, the second lens surface has a larger diameter than the first lens surface, the third lens surface has a diameter equal to or larger than that of the second lens surface, and the fourth lens surface has a larger diameter than the third lens surface.
According to such an arrangement, when light that has passed the first lens enters the second lens, it becomes possible to increase the amount of light that finally comes out of the fourth lens surface of the second lens toward the image formation region. Thus, it becomes possible to form a bright image.
Preferably, the fourth lens surfaces are connected together.
Such an arrangement is advantageous in increasing the diameter of the fourth lens surface and the amount of light coming out of the lens surface.
Preferably, the second lens array is provided with a recess isolating the fourth lens surfaces from each other.
According to such an arrangement, when light finally comes out of the fourth lens surface toward the image formation region, it becomes possible to efficiently prevent the optical cross talk between the second lenses, by using the recess.
A method of manufacturing a lens array provided by a second aspect of the present invention comprises a resin-body forming step of forming a resin component block of a translucent resin. The resin component block integrally includes a plurality of rows of lenses and supports holding the lenses. The method further comprises a dividing step of dividing the resin component block into a plurality of lens arrays each including a row of the lenses.
According to the lens array manufacturing method with such an arrangement, it becomes possible to efficiently mass produce the first and the second lens arrays of the lens array unit offered by the first aspect of the present invention. Further, since an overall size of the resin component block is larger than an individual lens array which is obtained finally, a cavity of the mold used for the formation of the resin component block can be make large. Therefore, when molten resin is injected into the cavity, the molten resin can flow smoothly making it possible for example to appropriately form a precision portion such as the lens.
Preferably, the resin component block has an outer edge surrounding a region formed with the lenses, and the outer edge has at least a portion thicker than the region formed with the lenses.
According to such an arrangement, when the resin component block is formed by means of the injection molding, it becomes possible to allow the molten resin to flow smoothly in a portion of the cavity that corresponds to the outer edges. This makes it easy to let the resin fill the entire cavity in the mold, and possible to perform more appropriately the formation of the resin component block.
Preferably, the method further comprises a light shield forming step of providing a light shield isolating the lenses from each other.
According to such an arrangement, it becomes possible to obtain a lens array capable of preventing the optical cross talk among the lenses.
Preferably, the light shield forming step includes a step of providing a recess isolating the lenses from each other in the resin component block, and a coating step of coating a surface which defines the recess, with a dark material.
Preferably, the recess is formed in the resin-body forming step.
Such an arrangement eliminates the need to perform a separate operation for providing the recess in the resin component block, making it possible to reduce the number of steps necessary for the manufacture of the lens array.
Preferably, the recess is formed by a mechanical machining performed to the resin component block.
Such an arrangement eliminates the need for providing a projection necessary for forming the recess. Therefore, it becomes possible to reduce a cost of the mold. Further, the arrangement also makes it possible to precisely machine the recess.
Preferably, the recess is formed by a laser machining performed to the resin body.
According to such an arrangement, essentially the same effect is achieved, as achieved in the above case of providing the recess by mechanical machining. Moreover, the laser machining allows more precise machining than in the mechanical machining, making it possible for example to form a narrower width of the recess than by the mechanical machining.
Preferably, the coating step includes: a step of applying a dark paint to the surface of the resin body which defines the recess and a lens surface adjacent to the recess, of each lens; and a step of removing the paint from the lens surface before the paint applied to the lens surface dries and hardens.
Such an arrangement facilitates an operation of coating the other portion of the resin component block than the lens surface.
Preferably, each lens has an outer circumferential surface rising from the first support.
Such an arrangement provides a height difference between the lens surface and the support, facilitating the paint removing operation from the lens surface.
An optical device offered by a third aspect of the present invention comprises image forming means which forms an image of an object at a predetermined place by focusing light from the object, and is characterized that the image forming means is provided by a lens array unit. Further, the lens array unit comprises: a including a plurality of first lenses each serving as a convex lens, and a first support holding the first lenses, the first lenses and the first support being formed integrally of a translucent resin; and a second lens array including a plurality of second lenses each serving as a convex lens, and a second support holding the second lenses, the second lenses and the second support being formed integrally of a translucent resin; and is characterized that the first and the second lens arrays are placed, one on the other, with each of the first lenses in alignment with a corresponding one of the second lenses on a same axis, for formation of a non-inverted, non-magnified image.
The optical device with such an arrangement offers the same effect as achieved by the lens array unit offered by the first aspect of the present invention.
Preferably, the optical device further comprises: a light source for illuminating a document; and a plurality of light receiving elements each having a photoelectric transfer capability. Further, in this device, the image of the document is formed on the light receiving elements by having light reflected by the document focus through the lens array unit.
According to such an arrangement, the image of the document can be appropriately read without inversion nor magnification by the light receiving elements.
Preferably, the light receiving elements are disposed in a row in a predetermined direction, and each plurality of the first and the second lenses are disposed in a plurality of rows in the predetermined direction. Further, a path to the lens array unit from a place where the document is placed is intersected by a divergent lens diverging light from the document in a direction across the predetermined direction.
According to such an arrangement, flux of the light which travels from the document toward the lens array unit has a narrow angle (angle of view) in the direction across the predetermined direction. As a result, it becomes possible to give the first and the second lenses a greater depth of focus, leading to such an advantage that the image is less prone to becoming out of focus. And of course, a bright image can be obtained by a plurality of arrays of the first and the second lenses.
Preferably, the optical device further comprises a transparent plate capable of guiding the document, and the transparent plate is formed integrally with the divergent lens.
According to such an arrangement, it becomes possible to reduce increase in the number of parts.
Preferably, the optical device further comprises a divergent lens disposed between the lens array unit and the light receiving elements for divergence of light having passed the lenses of the lens array in a direction across the predetermined direction.
According to such an arrangement, it becomes possible to narrow the angle of focusing flux of the light which travels from the lens array unit toward the light receiving elements. Therefore, even if there is a distance error between the lens array unit and the light receiving elements due to an assembling error of the optical device, it is still possible to form a well-focused image.
Preferably, the optical device comprises: at least one image display disposed in front of the lens array unit;
a translucent screen disposed behind the lens array unit; and an auxiliary lens disposed between the screen and the lens array unit. An image displayed in the image display is enlarged or reduced into a non-inverted image on the screen by the lens array unit and the auxiliary lens.
According to such an arrangement, an enlarged non-inverted image or reduced non-inverted image of the image displayed in the image display can be displayed on the screen.
Preferably, the optical device comprises a plurality of the image displays, and further, the auxiliary lens is provided by a divergent lens, whereby images displayed in the respective image displays are enlarged into an integrated non-inverted image on the screen.
According to such an arrangement, it becomes possible to form a desired enlarged view on the screen, without projecting an image of the region where the image displays are connected together.
Preferably, the screen is provided by a color filter including a filter element for each color of red, green and blue.
According to such an arrangement, it becomes possible to obtain an image having a high contrast on the screen. Specifically, unlike the above arrangement, if a white screen is used, it is difficult to clearly present the color black because the background color of the image projected is white. On the contrary, according to the above arrangement, a variety of colors can be created by a color additive process of red, green and blue, and further, these colors are not presented on a white background. Therefore, it is possible to increase contrast of the image.
Preferably, a surface of the screen away from the auxiliary lens is convex or concave.
According to such an arrangement, the surface of the screen on which the image is displayed becomes visible from an octagonal direction of the screen, making it possible to display at a wide angle of view.